Review of stationary and transport CO2 refrigeration and air conditioning technologies

Since its resurgence as a refrigerant in the 1990s, Carbon Dioxide (CO2) has grown in popularity and breadth of application. Its negligible global warming potential (GWP) eliminates the risk of being phased out due to legislation, and its non-toxicity, non-flammability, and low cost allows its use in many vapor compression cycle applications. However, the high critical pressure and low critical temperature require significantly more compressor power under moderate and high-ambient conditions and thus, necessitate the addition of cycle modifications to reach coefficient of performance (COP) values equal to or greater than those of other working fluids. This paper provides a review of research conducted on the use of CO2 vapor compression cycles in refrigeration and air conditioning (AC) cycles for both transportation and stationary refrigeration. A primary intention of writing this review is to offer evidence and justification for many common cycle modifications, then connect these modifications to a broad array of applications. Thus, advanced cycles in mobile and stationary applications are shown and the individual modifications present have their own independent justification to create a complete picture of the topic. The designs of complete systems, as well as specific components within the system, are included, as are the relations between the thermo-physical properties of CO2 and their benefits in these particular applications. Additionally, economic analyses of the feasibility of using CO2 in place of existing fluids are reviewed. Challenges facing the use of CO2 refrigeration cycles in stationary and transportation refrigeration are discussed, as are potential future advancements to overcome them.

Automated summary

CO2 has gained popularity as a refrigerant due to its low global warming potential, non-toxicity, non-flammability, and low cost. However, it requires more compressor power under moderate and high-ambient conditions, necessitating cycle modifications to achieve comparable coefficient of performance values.